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PART 2: SAN JUAN COUNTY CHARACTERIZATION REPORT
CHAPTER 6: DESCRIPTIONS OF THE INDIVIDUAL PRIORITY WATERSHEDS
East Sound | Friday Harbor | Westcott/Garrison Bays | Fisherman Bay | Roche Harbor |
Mud/Hunter Bays | West Sound | Deer Harbor | False Bay
The False Bay watershed was ranked 9th in the 1988 San Juan County Watershed Ranking Report. It contains the most extensive grassland acreage as well as the most actively used farmland in the county. It is the largest drainage basin of all the watersheds in the county and includes the water supply source for the Town of Friday Harbor. This extensive drainage system (11,697 acres) terminates in the relatively small receiving waters (232 acres) of False Bay.
False Bay is a marine biological preserve belonging to the University of Washington Friday Harbor Laboratories. The Labs own 200 acres of tidelands and uplands at the bay. This area is used extensively for research purposes.
False Bay consists of a large area of tidal flats which, in conjunction with the upland wildlife preserve, provide excellent habitat for a high diversity of plants, birds, and sea life, including many intertidal species generally found on the open coast (Giant Green Anemones, Gooseneck Barnacles, and California Mussels). False Bay has no recreational or commercial fishing or shellfish harvest. Abalone and sea urchins have been harvested in the past in the outer coastal waters of the watershed. Due to its shallow nature and status as a preserve there is no boating activity.
Substantial eel grass beds and kelp beds are located at the mouth and along the coastline adjacent to the bay. Nearby areas are used as seal haul-outs. There are numerous breeding, nesting, and wintering sites for an abundance of resident and migratory birds in the watershed. These birds utilize the shoreline, tidelands, and freshwater wetlands, as well as forested uplands.
The False Bay watershed has the greatest extent of identified wetland acreage of all the watersheds in the county. A significant portion of the watershed is a surface water resource area. There are at least two streams of significance draining to False Bay with numerous tributaries stemming from all portions of the watershed. The largest creek, San Juan Creek, is the only Class 2 creek in the county.
The False Bay watershed has several notable areas that are examples of native ecosystems including grassland Oak-savannah communities and open woodlands. The knoll of Cady Mountain which provides part of the watershed boundaries has been classified as having high regional significance by the Nature Conservancy (1975). Some of the oak trees found there are estimated to be 400 years old. Some more unusual terrestrial island wildlife have important habitat in the upland areas of the watershed including the Northern Alligator Lizard, Purple Martins, and Trumpeter swans.
Trout Lake is located in this watershed and is the main water supply for the town of Friday Harbor, and supplies water to a large portion of the island's population. It is the largest Class 1 type water body on San Juan Island. Lawson Lake is a 12.5 acre Class 1 type water body that augments Friday Harbor's water supply. Wood reservoir is a 29 acre, Class 2 impoundment. Zylstra Lake is 70 acres and was created to provide irrigation water. There also are several Class 2 through 5 water bodies less than 5 acres in size.
Agricultural uses in False Bay are continuing their historical presence although more land is being converted to rural-residential use with farming occurring on smaller acreages. Livestock operations include sheep, cattle, and horses primarily. A field survey in the winter of 1997-98 revealed that most fields were in fair condition, but some overgrazing and poor management was apparent. During the winter most of the fields at the valley bottom are saturated with standing pools of water. In some cases animals are being pastured through the winter with access to the creeks and saturated areas.
Most of the length of San Juan Valley Creek is unprotected with little canopy cover. The creek flows through agriculture lands with a residential density of 40 acres per unit. The remainder of the watershed has a density potential of 5 acres per unit with some sections in the upper areas designated for 10 acres per unit.
There are upland areas with high erosion potential and on-site septic suitability is poor in all of the watershed. Traffic in the False Bay watershed is lower than in many other watersheds as there are no significant tourist destinations.
Several reaches of both streams leading to False Bay were sampled during May and June of 1997. San Juan Valley Creek, the major drainage to False Bay, was found to have fecal coliforms exceeding State standards in two locations sampled, both in the lower watershed area. One of the sites was monitored for six weeks between November 1997 and February of 1998. During that period four of six samples exceeded 50 colonies/100mL. (See Chapter 5, Water Quality, for more information about these results.) Fecal contamination of a community water system well was documented in the upper watershed in 1999. The suspected source is a failing septic system. (SJC Health and Community Services)
The land use adjacent to San Juan Valley Creek and upstream from the sampling locations is largely agriculture. The creek runs through several agricultural fields and is unfenced for most of its route, leaving it accessible for animal use. The drainage area is highly saturated for a significant portion of the year due to runoff from the surrounding hills and the generally low-lying topography of the basin floor. In such conditions, water in the pastures can essentially be flowing through and on top of the soil. Both livestock and failing septic systems are concerns for sources of fecal contamination in this area.
Landcover Vegetation Current Land Use*
12% Dense Forest
26% Timber Land
30% Sparse Forest
18% Residential parcels (414)
23% Wetlands Public Lands
Marine and intertidal
Lakes Designated Growth Areas No Class 1 Trout
Class 1 Lawson
Upland Native Ecosystem Yes Class 2 Woods
Class 2 Zylstra
Critical Marine Habitat Yes Lakes and Freshwater Wetlands 6% Streams
Surface Water Resource Area Yes Class 3
Research/Education Areas Yes Drainage runoff
*Current land use information is from the County Assessor's records.
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